XBCF is a container format designed for indexed block compression on Amazon S3 or similar distributed storage systems with high seek latencies. It supports the following features:* Configurable compression codec* Configurable block encryption codec* Seeking support, with granularity equal to the compression block size (1MB by default)* Recursive encapsulation of XBCF containers * Multiple worker nodes can independently upload parts of the same multi-part upload, each formatted as XBCF * At close time, a higher-level XBCF is concatenated from the parts